Answer: x = g - c
Explanation:
Ok, since we don't know the variables it is going to be outside of the box question. We need to create another equation that equals this equation. The way to do that is to move the variable to 1 side. Think of the = sign as a line, then move the c across the line with a rule that "Crossing the line would make that variable negative." So from positive c, it goes to -c meaning we would subtract it from g.
g = c + x
g - c = x
x = g - c